Techniques for integrated preheating and coating of powder material in additive fabrication and related systems and methods

ABSTRACT

Techniques for improved efficiency of sintering in additive fabrication are described. According to some aspects, mechanisms for depositing and leveling source material are combined with a mechanism for heating the material. In some embodiments, one or more heating elements may be arranged to lead and/or follow a material deposition mechanism such that heat may be applied to the build region in concert with deposition of material. As a result of this technique, the heating and depositing steps may be performed closer together in time and/or heat may be applied more directly to the material than in conventional systems. As a result, greater control over material temperature may be achieved, thereby avoiding excess temperature exposure and subsequent undesirable changes to the material.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. § 119(e) ofU.S. Provisional Patent Application No. 62/575,024, filed Oct. 20, 2017,titled “Techniques For Integrated Preheating And Coating Of PowderMaterial In Additive Fabrication And Related Systems And Methods,” whichis hereby incorporated by reference in its entirety.

BACKGROUND

Additive fabrication, e.g., 3-dimensional (3D) printing, providestechniques for fabricating objects (also referred to as “parts”) bycausing portions of a building material to solidify at specificlocations. Additive fabrication techniques may includestereolithography, selective or fused deposition modeling, directcomposite manufacturing, laminated object manufacturing, selective phasearea deposition, multi-phase jet solidification, ballistic particlemanufacturing, particle deposition, selective laser sintering orcombinations thereof. Many additive fabrication techniques build partsby forming successive layers, which are typically cross-sections of thedesired object. Typically each layer is formed such that it adheres toeither a previously formed layer or a substrate upon which the object isbuilt.

In one approach to additive fabrication, known as selective lasersintering, or “SLS,” solid objects are created by successively formingthin layers by selectively fusing together powdered material. Oneillustrative description of selective laser sintering may be found inU.S. Pat. No. 4,863,538, incorporated herein in its entirety byreference.

SUMMARY

According to some aspects, an additive fabrication device configured toproduce three-dimensional objects by sintering a source material isprovided, the device comprising a material deposition mechanism, afabrication bed configured to receive source material from the materialdeposition mechanism, a heater configured to move over the fabricationbed and to direct heat onto the source material deposited by thematerial deposition mechanism, and an energy source configured to bedirected onto the deposited source material heated by the heater tocause sintering of the heated deposited source material.

According to some aspects, a method of fabricating an object viaadditive fabrication is provided, said additive fabrication comprisingsintering a source material, the method comprising moving a materialdeposition mechanism over a fabrication bed and operating the materialdeposition mechanism to deposit source material onto the fabricationbed, directing heat from the heater onto the source material depositedby the material deposition mechanism by moving a heater over thefabrication bed, and sintering the heated deposited source material bydirecting an energy source onto the deposited source material heated bythe heater.

The foregoing apparatus and method embodiments may be implemented withany suitable combination of aspects, features, and acts described aboveor in further detail below. These and other aspects, embodiments, andfeatures of the present teachings can be more fully understood from thefollowing description in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Various aspects and embodiments will be described with reference to thefollowing figures. It should be appreciated that the figures are notnecessarily drawn to scale. In the drawings, each identical or nearlyidentical component that is illustrated in various figures isrepresented by a like numeral. For purposes of clarity, not everycomponent may be labeled in every drawing.

FIG. 1 depicts an illustrative selective laser sintering device,according to some embodiments;

FIG. 2 depicts an illustrative selective laser sintering device in whichheating and material deposition mechanisms are combined, according tosome embodiments;

FIG. 3 depicts an illustrative combined heating and material depositionassembly, according to some embodiments;

FIG. 4 depicts an illustrative selective laser sintering device in whichheating and material deposition mechanisms are combined with an energysource, according to some embodiments;

FIG. 5A depicts an overhead view of a rotational assembly, according tosome embodiments;

FIG. 5B depicts the rotational assembly of FIG. 5A within anillustrative selective laser sintering device, according to someembodiments;

FIG. 6A-B depict two different views of an assembly that combinesinfrared sensors with a heating array, according to some embodiments;

FIG. 7 is a block diagram of a system suitable for practicing aspects ofthe invention, according to some embodiments; and

FIG. 8 illustrates an example of a computing system environment on whichaspects of the invention may be implemented.

DETAILED DESCRIPTION

Some additive fabrication techniques, such as Selective Laser Sintering(SLS), form parts by fusing source material, such as one or more finepowders, together into larger solid masses. This process of fusing asource material is referred to herein as “consolidation,” and typicallyoccurs by directing sufficient energy (e.g., heat and/or light) to thematerial to cause consolidation. Some energy sources, such as lasers,allow for direct targeting of energy into a small area or volume. Otherenergy sources, such as heat beds or heat lamps, direct energy into acomparatively broader area or volume of material. Since consolidation ofsource material typically occurs at or above a critical temperature,producing parts as intended requires effective management of temperaturewithin the source material.

In order to form a part via sintering techniques from a plurality oflayers, a layer of unconsolidated material is deposited onto afabrication bed and then heated in desired locations to consolidateregions of the layer. An additional layer of unconsolidated material isthen deposited onto the fabrication bed over the first layer and furtherregions consolidated, and so forth until the part is formed.

In some additive fabrication systems, the unconsolidated source materialis preheated to a temperature that is sufficiently high so as to requireminimal additional energy exposure to trigger consolidation. Forinstance, some conventional systems utilize radiating heating elementsthat aim to consistently and uniformly heat both the uppermost layer andthe volume of the material to a temperature below, but close to, thecritical temperature for consolidation. A laser beam or other energysource directed at the material may then provide sufficient energy toreach the critical temperature and thereby cause consolidation. However,maintaining an elevated temperature in this manner prior toconsolidation, sometimes referred to as “preheating,” poses numeroustechnical challenges.

Consistency of the temperature of preheated unconsolidated material maybe critical to the successful fabrication of parts using the selectivesintering process. In particular, the system should preferably maintainthe temperature of the preheated unconsolidated material at as close toa constant temperature as feasible so that the total amount of energyactually delivered to an area of unconsolidated material can bepredicted for a given energy exposure amount. Additionally, whenconsolidating the material, the system should preferably maintain thetemperature of the material at or above its consolidation temperaturefor a sufficient time for the consolidation process to complete.Moreover, underheating of the material during fabrication may result ina failure of the material to consolidate and/or may result in inferiormaterial properties within the fabricated part. As a result of thesefactors, consistent and even preheating of the unconsolidated materialis highly desirable.

While conventional systems may employ numerous heating techniques, suchas radiative or convective heating methods, such systems generallydeposit unconsolidated material in a build region then wait for theunconsolidated material to be heated to an even temperature beforeperforming consolidation. These heating techniques can significantlyincrease the amount of time needed to fabricate a part, since a waitingperiod must be performed prior to forming each layer of the part. Someconventional systems attempt to reduce this waiting period by heatingthe unconsolidated material prior to its deposition into the buildregion, but this may have the undesirable effect of degrading theunconsolidated material by exposing it to high temperatures for anextended period of time. Additionally, excessive heating of the materialprior to deposition can lead to diminished flow characteristics whichmay cause the bed to tear or reduce the smoothness of coating as thematerial is deposited.

The inventors have recognized and appreciated that efficiency of asintering additive fabrication process may be increased by combining amechanism for depositing and leveling unconsolidated material with amechanism for heating the unconsolidated material. In particular, one ormore heating elements may be arranged to lead and/or follow a materialdeposition mechanism such that heat may be applied to the build regionin concert with deposition of material. As a result of this technique,the heating and depositing steps may be performed closer together intime and/or heat may be applied more directly to the material than inconventional systems. As a result, greater control over materialtemperature may be achieved, thereby avoiding excess temperatureexposure and subsequent undesirable changes to the material.

According to some embodiments, a heating element and a materialdeposition mechanism may be arranged in an additive fabrication deviceso that both can be moved simultaneously over a fabrication bed. Theheating element may be arranged to pass over areas of the fabricationbed at the same time, or shortly after, the material depositionmechanism passes over the same areas. In some embodiments, the heatingelement and material deposition mechanism may be mechanically coupledtogether (e.g., attached to a common assembly). In some embodiments, theheating element and material deposition mechanism may be separatelymounted and operated but configured to move such that the heatingelement leads or follows the material deposition mechanism.

According to some embodiments, a heating element may be operated in aclosed loop feedback mode such that an amount of heating produced isselected based on sensing the temperature of one or more regions of thebuild region. In some embodiments, such sensing may be accomplished viathermal imaging and/or other non-contact thermal sensing means of thefabrication bed.

The herein-described techniques for combining a mechanism for depositingand leveling unconsolidated material with a mechanism for heating theunconsolidated material may, as discussed above, result in a sinteringadditive fabrication process with greater efficiency. Nonetheless, theinventors have additionally recognized and appreciated techniques forfurther increasing efficiency by combining the heating and depositionmechanisms with a mechanism for consolidating material. In particular,unconsolidated preheated material may be consolidated by an energysource that is arranged to follow the material deposition and heatingmechanisms and that is configured to direct energy to desired areas ofthe material. For instance, newly deposited and preheated material maybe consolidated by a laser while the material deposition and heatingmechanisms continue to move and prepare material in other areas of thefabrication bed.

In some embodiments, combined mechanisms for deposition, heating andconsolidation may be arranged to rotate such that these mechanisms movecontinuously (or moved continuously except for a period in which thefabrication bed is lowered). For instance, the mechanisms may rotatearound an axis such that they may be continuously moved in the samedirection (in contrast to moving from one end of a fabrication bed toanother, at which point the mechanisms must stop before reversingdirection). As a result, even greater efficiency of a sintering additivefabrication device may be achieved by forming consolidated materialcontinuously, or continuously except for a period in which thefabrication bed is lowered.

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, techniques for combining mechanisms fordepositing and preheating unconsolidated material in sintering additivefabrication techniques. It should be appreciated that various aspectsdescribed herein may be implemented in any of numerous ways. Examples ofspecific implementations are provided herein for illustrative purposesonly. In addition, the various aspects described in the embodimentsbelow may be used alone or in any combination, and are not limited tothe combinations explicitly described herein.

An illustrative conventional selective laser sintering (SLS) additivefabrication device is illustrated in FIG. 1. In the example of FIG. 1,SLS device 100 comprises a laser 110 paired with a computer-controlledscanner system 115 disposed to operatively aim the laser 110 at thefabrication bed 130 and move over the area corresponding to a givencross-sectional area of a computer aided design (CAD) model representinga desired part. Suitable scanning systems may include one or moremechanical gantries, linear scanning devices using polygonal mirrors,and/or galvanometer-based scanning devices.

In the example of FIG. 1, the material in the fabrication bed 130 isselectively heated by the laser in a manner that causes the powdermaterial particles to fuse (sometimes also referred to as “sintering” or“consolidating”) such that a new layer of the object 140 is formed. SLSis suitable for use with many different powdered materials, includingany of various forms of powdered nylon. In some cases, areas around thefabrication bed (e.g., the walls 132, the platform 131, etc.) mayinclude heating elements to heat the powder in the fabrication bed. Suchheaters may be used to preheat unconsolidated material, as discussedabove, prior to consolidation via the laser.

Once a layer has been successfully formed, the fabrication platform 131may be lowered a predetermined distance by a motion system (not picturedin FIG. 1). Once the fabrication platform 131 has been lowered, thematerial deposition mechanism 125 may be moved across the fabricationbed 130, spreading a fresh layer of material across the fabrication bed130 to be consolidated as described above. Mechanisms configured toapply a consistent layer of material onto the fabrication bed mayinclude the use of wipers, rollers, blades, and/or other levellingmechanisms for moving material from a source of fresh material to atarget location.

Since material in the powder bed 130 is typically only consolidated incertain locations by the laser, some material will generally remainwithin the bed in an unconsolidated state. This unconsolidated materialis sometimes referred to as a “part cake.” In some embodiments, the partcake may be used to physically support features such as overhangs andthin walls during the formation process, allowing for SLS systems toavoid the use of temporary mechanical support structures, such as may beused in other additive manufacturing techniques such asstereolithography. In addition, this may further allow parts with morecomplicated geometries, such as moveable joints or other isolatedfeatures, to be printed with interlocking but unconnected components.

The above-described process of producing a fresh layer of powder andconsolidating material using the laser repeats to form an objectlayer-by-layer until the entire object has been fabricated. Once theobject has been fully fabricated, the object and the part cake may becooled at a controlled rate so as to limit issues that may arise withfast cooling, such as warping or other distortion due to variable ratecooling. The object and part cake may be cooled while within theselective laser sintering apparatus, or removed from the apparatus afterfabrication to continue cooling. Once fully cooled, the object can beseparated from the part cake by a variety of methods. The unusedmaterial in the part cake may optionally be recycled for use insubsequent fabrication.

As discussed above, it is highly desirable in a system such as system100 shown in FIG. 1 to wait for unconsolidated material that isdelivered onto the fabrication bed to reach a consistent temperaturebefore consolidating the material with the laser. This waiting period,which is performed for each layer of the object being fabricated,increases the time needed to fabricate the object.

FIG. 2 depicts an illustrative selective laser sintering device in whichheating and material deposition mechanisms are combined, according tosome embodiments. In illustrative system 200 shown in FIG. 2, the laseror scanning system is omitted for clarity, however such a system couldinclude these or another suitable energy source for consolidatingpreheated source material.

In the example of FIG. 2, a preparatory assembly 250 is configured tomove over the fabrication bed 230 and includes a heating mechanism 251and a deposition mechanism 252. As the preparatory assembly 250 moves,the deposition mechanism deposits unconsolidated material onto thefabrication bed, while the heating mechanism follows the depositionmechanism and heats the just-deposited material. As a result, heatingand depositing of material are performed closer together in time andheat is applied more directly to unconsolidated material compared toconventional systems that employ preheating (e.g., compared to thesystem 100 shown in FIG. 1).

According to some embodiments, heating mechanism 251 may include anyelectrically driven heating element or elements, including but notlimited to one or more quartz tube heaters, ceramic heaters, heatingcoils, polymer PTC heaters, metal heaters (e.g., Nichrome, resistancewire, etched foil), or combinations thereof. The additive fabricationdevice 200 may include a controller configured to drive the heatingmechanism to produce a desired amount of heat. While the illustrativeexample of FIG. 2 shows the heating mechanism 251 trailing the materialdeposition mechanism 252 (i.e., the heating mechanism is arranged topass over material subsequent to its deposition), it will be appreciatedthat the heating mechanism may also be positioned to lead the materialdeposition mechanism 252 (i.e., the heating mechanism is arranged topass over already-consolidated material subsequent to unconsolidatedmaterial being deposited over it). In some embodiments, heatingmechanisms may be placed so as to both lead and trail the materialdeposition mechanism.

In some embodiments, heating elements other than the heating mechanism251 may be embedded within, or otherwise thermally coupled to, thematerial deposition mechanism 252. In some embodiments, such heatingelements may be disposed within a levelling mechanism (e.g., a roller)to heat or maintain the levelling mechanism at a desired temperature.The levelling mechanism, such as a roller, may then be placed intocontact with the fabrication bed 230, including newly depositedmaterial, in order to increase, or decrease, the temperature of theportion of the fabrication bed contacted by the heated portion of thematerial deposition mechanism primarily via conductive heating.

In some cases, a heated levelling mechanism may not convey a desiredamount of thermal energy into the fabrication bed. For instance, thelevelling mechanism may not have sufficient contact with the fabricationbed and/or the levelling mechanism may be heated at a low intensity toavoid clumping and other material changes at the fabrication bed duringthe application of levelling means. In such cases, it may beadvantageous for the deposition mechanism to include more than onelevelling mechanism. These levelling mechanisms may be arranged tocontact the surface of the fabrication bed in series as the preparatoryassembly moves, with each such mechanism being maintained at an elevatedtemperature with respect to the fabrication bed 230. In someembodiments, the additive fabrication device 200 may include one or moreheating elements positioned to convey or direct heat through one or moredevices or orifices associated with the material deposition mechanism252, or so as to maintain one or more components of the materialdeposition mechanism at a temperature different than the surroundingenvironment. Such heat may be conducted via conduction or flow of gas orfluid into or through the material deposition mechanism.

In some embodiments, heated gas or fluid may be directed onto thefabrication bed 230 and/or onto material in transit from the materialdeposition mechanism 252 to the fabrication bed to increase thetemperature of the material via convection.

It will be appreciated that the various heating techniques describedabove, including heating unconsolidated material via the heatingmechanism 251 and heating some or all of the deposition mechanism viaheating elements positioned within or near to the deposition mechanism,may be employed in any suitable combination so that desired temperaturesof unconsolidated material and of the fabrication bed may be achieved.

According to some embodiments, deposition mechanism 252 may includevarious forms of dispensing mechanisms, including but not limited tohoppers, fluidized powder transport tubing, mechanical augers, orcombinations thereof. Such dispensing mechanism may further comprisedosing or other mechanism for regulating the amount of materialdispensed through the deposition process, such as mechanical apertures,calibrated augers, rotating paddles, or other means known in the art. Insome embodiments, the deposition mechanism may include one or moreleveling mechanisms to produce a level layer of material afterdeposition. Such leveling mechanisms may include one or more wipers,rollers, blades, or combinations thereof.

FIG. 3 depicts an illustrative combined heating and material depositionassembly, according to some embodiments. Illustrative assembly 303includes heating elements 301 positioned either side of a materialdeposition mechanism 302 within a frame 306. The view shown in FIG. 3 ispositioned to face down onto fabrication bed 304. The frame 306 isconfigured to move across the fabrication bed 304 along axis 305, sothat some or all of the heating elements 301 pass over areas of thefabrication bed 304 at the same time as, or shortly after, the passageof the material deposition mechanism 302 due to the combined motion ofthe preparatory assembly 303.

In the example of FIG. 3, combined motion of the heating elements 301and material deposition mechanism 302 is achieved by mechanicallymounting or coupling the heating elements to the material depositionmechanism by attaching each to frame 306. It will be appreciated thatthe heating elements 301 and material deposition mechanism 302 could, inother embodiments, be coupled to separate frames and moved independentlyover the fabrication bed.

In some embodiments, heating elements 301 may be mounted to the frame306 such that a lower surface of the heating element moves parallel tothe topmost surface of the fabrication bed 304, including any newlydeposited material, at a predefined separation distance. In general, itmay be advantageous to minimize such separation distances, in order tooptimize the efficiency of heat application. Too close a proximity tothe fabrication bed may increase the risk of particulates or othermaterial from the fabrication bed coating, contaminating, or otherwiseinterfering with the heating element. Moreover, proximity to thefabrication bed may increase the degree to which non-uniformities in theheating element's production of heat result in non-uniformities inheating the fabrication bed. In some embodiments, the inventors havefound separation distances between a heat element and the fabricationbed in the range of 0.1 mm-50 mm to be acceptable, with furtheroptimization by routine testing of specific material types and heatsources. In some embodiments, one or more shrouds (not shown) may beadded to the frame (or otherwise positioned around either or bothheating elements) to direct thermal energy from the heating elementstowards the powder surface, rather than to other areas or components ofthe device.

FIG. 4 depicts an illustrative selective laser sintering device in whichheating and material deposition mechanisms are combined with an energysource, according to some embodiments. In the example of FIG. 4, apreparatory assembly 450 is configured to move over the fabrication bed430 and includes a heating mechanism 451, a material depositionmechanism 452, and an energy source 453. As the preparatory assembly 450moves, the material deposition mechanism 452 deposits unconsolidatedmaterial onto the fabrication bed, while the heating mechanism followsthe deposition mechanism and heats the just-deposited material.Furthermore, the unconsolidated preheated material is then consolidatedby energy source 453. As a result, heating and depositing of materialare performed closer together in time and heat is applied more directlyto unconsolidated material compared to conventional systems that employpreheating (e.g., compared to the system 100 shown in FIG. 1). Inaddition, consolidation can occur a very short time after preheating dueto the physical proximity of the heating mechanism 451 and the energysource 453.

Heating mechanism 451 and deposition mechanism 452 may be configured inany of the numerous ways described above with respect to heatingmechanism 251 and deposition mechanism 252 shown in FIG. 2. In someembodiments, energy source 453 may include a laser and scanning systemand direct laser light onto the fabrication bed via the energy source.It will be appreciated that the energy source 453 may not necessary bethe ultimate source of the energy so long as the energy from an initialsource can be directed to the preparatory assembly to be directed ontothe fabrication bed. For instance, energy source 453 may comprise a lensand/or an optical fiber mounted to the preparatory assembly 450 that iscoupled to a laser source that is not mounted to the preparatoryassembly but that can be operated to direct light to the lens and/oroptical fiber.

In the example of FIG. 4, the preparatory assembly is configured to movefrom across the fabrication bed, which results in a necessary stop atthe exterior of the bed once the preparatory assembly reaches an edge ofthe bed. As discussed above, one approach to eliminate such stoppages isto rotate a preparatory assembly about an axis, thereby continuallymoving a deposition mechanism, heating mechanism and energy source.

FIG. 5A depicts an overhead view of one such illustrative rotationalassembly, according to some embodiments. In the example of FIG. 5A, apreparatory system is illustrated that comprises radial arms 503 and 505and axis 506. This system may be configured to rotate in a direction 507about the axis 506 at the center of an annular (or circular) fabricationbed 504. Alternatively, the fabrication bed 504 itself may be rotated indirection 507 about the axis 506 such that portions of the rotaryfabrication bed 504 pass under the preparatory system. In either case,the fabrication bed and preparatory system may be continuously movedrelative to one another. As a result, simultaneous recoating,preheating, and exposure of a fabrication bed may be performed, therebyreducing delays for repositioning or inactive transit of the preparatorysystem. FIG. 5B depicts a cross sectional view of the rotationalassembly of FIG. 5A within an illustrative selective laser sinteringdevice, according to some embodiments.

Upon completion of exposure of a given layer of the fabrication bed 504,the fabrication platform may be lowered, or preparatory system raised,to allow for the deposition of fresh unconsolidated material on thefabrication bed. Alternatively, the fabrication platform may be loweredat a gradual rate, or in stages during the fabrication process. Inparticular, it may be advantageous to include additional radialstructures 505 of the preparatory system, particularly when such systemsfurther include means of independently delivering focused energy to thefabrication bed 507. In such cases, production of parts may beaccelerated by having more than one radial arm simultaneously operate ondifferent sections of the fabrication bed 504. As portions of thefabrication bed 504 pass below each portion of the preparatory system,said system may distribute new material, level said material, and/orpreheat such material using included heating elements. And, whencombined with a source of focused energy, said preparatory system mayfurther expose new material to focused energy, causing consolidation,sintering, or other desirable material changes. The ability to conductsuch processes in parallel may advantageously allow for the productionof multiple separate objects simultaneously, for the production ofmultiple portions of the same object simultaneously, or for morecomplicated multiple step processing of the same portion of an object.

According to some embodiments, each of the illustrative portions 503 and505 of the preparatory system may each include one or more heatingelements, material deposition mechanisms and/or energy sources. In someembodiments, it may be beneficial to perform only some of the materialdeposition, preheating and consolidation acts with a given radial arm ofthe preparatory system. For instance, in the example of FIG. 5A,adjacent pairs of radial arms may include, in a first case, a materialdeposition and leveling mechanism in addition to a heating element, andin a second case, an energy source only. As a result, when in motion,the same point on the fabrication bed may have material deposited,leveled and preheated when a first radial arm passes the point, and thenundergo consolidation when the subsequent radial arm passes this point.

FIG. 6A-B depict two different views of an assembly that combinesinfrared sensors with a heating array, according to some embodiments. Asshown in the example of FIGS. 6A-B, a preparatory mechanism (not shown)may include one or more infrared sensors 608 arrayed across the width ofthe preparatory mechanism with a given spacing. Such sensors 608 may bearranged between a plurality of heating elements 609 and a levellingdevice 602.

As discussed above, it may be beneficial to sense the temperature of afabrication bed and determine how to most effectively apply heat viaheating element(s) based on the sensed temperature. Said determinationmay comprise operating one or more heating elements for a selectedlength of time and/or at a selected temperature based on the sensedtemperature. In the example of FIGS. 6A-B, according to someembodiments, each of the heating elements may be independently operatedbased on a temperature sensed by respective adjacent sensors. In thismanner, the heating elements in the array 609 may, in some embodiments,be operated at different temperatures and/or for different lengths oftime.

Any suitable control scheme may be employed to operate heating elements609 based on temperatures sensed by the sensors 608. In someembodiments, an “open loop” control scheme may be appropriate based uponcalculated or measured thermal characteristics of the larger system, soas to maintain a consistent and appropriate temperature for sintering atthe fabrication bed. In some embodiments, various types of “closed loop”control systems, such as PID control of heating elements, may beutilized based upon one or more sensors positioned within the heatingelements, material deposition mechanism, or other location.

In some embodiments, temperature sensing separate from the temperaturesensors 608 may be additionally or alternatively performed via thermalimaging or other non-contact thermal sensing means of the fabricationbed itself. In general, the application of heat from sources immediatelyproximate to the fabrication bed may allow for significantly moreefficient heating of material reducing both the peak and total powerconsumption of the device and also any unwanted secondary heating toother components of the device. Moreover, by applying heat more directlyto the material, additional control over material temperature may beachieved, avoiding excess temperature exposure and subsequent unwantedchanges to the material. In addition, while the embodiments describedabove have generally applied heat uniformly over the fabrication bed704, some embodiments of the present invention may include multipleheaters 709 or heating zones in order to provide more fine grainedcontrol over various regions of the fabrication bed 704. Such variableapplication of heat may be provided as a result of differences instarting temperature across the fabrication bed 704, such as may bedetermined via non-contact thermal sensing of sufficient resolution,such as thermal imaging.

In some embodiments, application of different amounts of heat (and/orapplication of heat for different lengths of time) may be determinedbased upon patterns of prior exposure and heating or upon plannedexposures and heating. As one example, previously sintered material mayprovide thermal energy to newly deposited material, such as discussed inU.S. Provisional Patent Application No. 62/545,231, filed on Aug. 14,2017, incorporated herein by reference. Accordingly less thermal energymay be applied onto newly distributed material overlaying previouslysintered material. Alternatively, more thermal energy may be applied tomaterial not overlaying such sintered material. In some embodiments,thermal energy may further be restricted to those portions of thefabrication bed expected to be sintered in the current or subsequentprocess steps. As one example, fabrication processes only exposing thecenter region of a larger fabrication bed may benefit from theapplication of heat to said center region and a sufficient margindistance.

According to some embodiments, it may be advantageous to arrange theheating elements 609 such that the sensors 608 pass over a given area ofthe fabrication bed 604 in advance of the heating elements 609, in orderto determine the appropriate degree of heating based upon the sensedheat. In some embodiments, such as described above in relation to FIG. 3in the context of two rows of heaters, it may be advantageous to includemultiple rows of sensors 608 such that the preparatory mechanism may beoperated in more than one direction. In other embodiments, it may alsobe advantageous to have multiple rows of sensors 608 to increase theeffective resolution or accuracy of measurements of temperatures fromthe fabrication bed 604. Alternatively, multiple rows of sensors 608 mayallow for measurement of temperature both prior to and followingexposure of the fabrication bed 604, thus allowing for improvedcalibration or detection of conditions requiring corrective steps suchas additional passes, delay periods, or process suspension.

In some embodiments, the spacing between each of the infrared sensors608 may be chosen at least in part based upon the field of view of theinfrared sensor 608, such that each infrared sensor 608 measures theinfrared emissions of a separate area of the fabrication bed 604. Aswill be appreciated, infrared sensors 608 may then be used to measurefabrication bed 604 temperature with an approximate resolution of saidspacing in one direction and arbitrary resolution in the direction ofmotion of the preparatory mechanism. In other embodiments, however, suchinfrared sensors 608 may be spaced so as to cause a desired degree ofoverlap of fields of view. In some embodiments, the number and spacingof infrared sensors 608 may be the same as the number as spacing ofheaters 609. To the extent that a heater 609 has a greater field widthin its thermal emissions than the infrared sensor 608 has field of view,however, it may be advantageous to have a reduced number of heaters 609.

Various alterations, modifications, and improvements are intended to bepart of this disclosure and within the spirit and scope of theinvention. As one example, although embodiments disclosed herein abovemay be disclosed in terms of a moving preparatory mechanism and astationary fabrication bed, it should be understood that the essentialcharacteristic of such motion is relative and not absolute, and thusthat other embodiments may be arranged such that the fabrication bed isinstead moved while the preparatory is stationary, or further that bothcomponents may be motion with an effective relative motion with respectto one another. Further, while embodiments discussed above may bediscussed in connection with the use of heat, it should be understoodthat maintaining a desired temperature in material may also include theuse of cooling elements, or elements capable of both heating andcooling, such as, for example, the use of one or more Peltier junctionswithin a levelling means.

Although the embodiments discussed herein may relate to selectivesintering technology, it should be understood that other embodimentswithin the scope of the invention may be advantageous in otherprocesses, such as high-speed sintering, inhibition sintering,three-dimensional printing, multi-jet modelling, or multi-jet fusionmodeling. In some such embodiments, for example, a second liquidmaterial may be added to newly deposited first material in order tomodify various characteristics of said first material, includingcohesiveness, color, or the degree and temperature at which saidmaterial must reach to consolidate or otherwise transform in asubsequent step. In these embodiments, one or more means for thedelivery of a second material, such as a liquid or powdered substance,may be provided for in connection with the preparatory mechanism. As oneexample, one or more nozzles or orifices, such as inkjet-typedispensers, may be located across the width of the preparatorymechanism. On other instances, such dispensers may be mounted onto oneor more heads capable of reciprocal motion along the width of thepreparatory mechanism. In such cases, it may be advantageous to positionheating elements, such as described above, so that heat is applied tothe fabrication bed following deposition so as to modify the temperatureof second material or otherwise induce a temperature-related change ofstate, such as evaporation of a solvent. Alternatively, it may beadvantageous to preheat the first material, as discussed above, prior tothe addition of the second material. Other modifications and methods ofmanufacturing will be obvious to those skilled in the art. Suchmodifications are intended to be part of this disclosure, and areintended to be within the scope of the invention.

FIG. 7 is a block diagram of a system suitable for practicing aspects ofthe invention, according to some embodiments. System 700 illustrates asystem suitable for generating instructions to perform additivefabrication by a device utilizing a combined material depositionmechanism and heating mechanism, and subsequent operation of theadditive fabrication device to fabricate an object. For instance,instructions to fabricate the object using an additive fabricationdevice, such as device 200 shown in FIG. 2 or device 400 shown in FIG.4, may comprise instructions to operate a heating mechanism in concertwith a deposition mechanism. In some cases, the instructions may also,when executed by the additive fabrication device, cause the additivefabrication device to operate an energy source in concert with theheating mechanism and deposition mechanism.

According to some embodiments, computer system 710 may execute softwarethat generates two-dimensional layers that may each comprise sections ofthe object. Instructions may then be generated from this layer data tobe provided to an additive fabrication device, such as additivefabrication device 720, that, when executed by the device, fabricatesthe layers and thereby fabricates the object. Such instructions may becommunicated via link 715, which may comprise any suitable wired and/orwireless communications connection. In some embodiments, a singlehousing holds the computing device 710 and additive fabrication device720 such that the link 715 is an internal link connecting two moduleswithin the housing of system 700.

FIG. 8 illustrates an example of a suitable computing system environment800 on which the technology described herein may be implemented. Forexample, computing environment 800 may form some or all of the computersystem 710 shown in FIG. 7. The computing system environment 800 is onlyone example of a suitable computing environment and is not intended tosuggest any limitation as to the scope of use or functionality of thetechnology described herein. Neither should the computing environment800 be interpreted as having any dependency or requirement relating toany one or combination of components illustrated in the exemplaryoperating environment 800.

The technology described herein is operational with numerous othergeneral purpose or special purpose computing system environments orconfigurations. Examples of well-known computing systems, environments,and/or configurations that may be suitable for use with the technologydescribed herein include, but are not limited to, personal computers,server computers, hand-held or laptop devices, multiprocessor systems,microprocessor-based systems, set top boxes, programmable consumerelectronics, network PCs, minicomputers, mainframe computers,distributed computing environments that include any of the above systemsor devices, and the like.

The computing environment may execute computer-executable instructions,such as program modules. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types. Thetechnology described herein may also be practiced in distributedcomputing environments where tasks are performed by remote processingdevices that are linked through a communications network. In adistributed computing environment, program modules may be located inboth local and remote computer storage media including memory storagedevices.

With reference to FIG. 8, an exemplary system for implementing thetechnology described herein includes a general purpose computing devicein the form of a computer 810. Components of computer 810 may include,but are not limited to, a processing unit 820, a system memory 830, anda system bus 821 that couples various system components including thesystem memory to the processing unit 820. The system bus 821 may be anyof several types of bus structures including a memory bus or memorycontroller, a peripheral bus, and a local bus using any of a variety ofbus architectures. By way of example, and not limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, MicroChannel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus.

Computer 810 typically includes a variety of computer readable media.Computer readable media can be any available media that can be accessedby computer 810 and includes both volatile and nonvolatile media,removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes volatile andnonvolatile, removable and non-removable media implemented in any methodor technology for storage of information such as computer readableinstructions, data structures, program modules or other data. Computerstorage media includes, but is not limited to, RAM, ROM, EEPROM, flashmemory or other memory technology, CD-ROM, digital versatile disks (DVD)or other optical disk storage, magnetic cassettes, magnetic tape,magnetic disk storage or other magnetic storage devices, or any othermedium which can be used to store the desired information and which canaccessed by computer 810. Communication media typically embodiescomputer readable instructions, data structures, program modules orother data in a modulated data signal such as a carrier wave or othertransport mechanism and includes any information delivery media. Theterm “modulated data signal” means a signal that has one or more of itscharacteristics set or changed in such a manner as to encode informationin the signal. By way of example, and not limitation, communicationmedia includes wired media such as a wired network or direct-wiredconnection, and wireless media such as acoustic, RF, infrared and otherwireless media. Combinations of the any of the above should also beincluded within the scope of computer readable media.

The system memory 830 includes computer storage media in the form ofvolatile and/or nonvolatile memory such as read only memory (ROM) 831and random access memory (RAM) 832. A basic input/output system 833(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 810, such as during start-up, istypically stored in ROM 831. RAM 832 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 820. By way of example, and notlimitation, FIG. 8 illustrates operating system 834, applicationprograms 835, other program modules 836, and program data 837.

The computer 810 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 8 illustrates a hard disk drive 841 that reads from or writes tonon-removable, nonvolatile magnetic media, a flash drive 851 that readsfrom or writes to a removable, nonvolatile memory 852 such as flashmemory, and an optical disk drive 855 that reads from or writes to aremovable, nonvolatile optical disk 856 such as a CD ROM or otheroptical media. Other removable/non-removable, volatile/nonvolatilecomputer storage media that can be used in the exemplary operatingenvironment include, but are not limited to, magnetic tape cassettes,flash memory cards, digital versatile disks, digital video tape, solidstate RAM, solid state ROM, and the like. The hard disk drive 841 istypically connected to the system bus 821 through a non-removable memoryinterface such as interface 840, and magnetic disk drive 851 and opticaldisk drive 855 are typically connected to the system bus 821 by aremovable memory interface, such as interface 850.

The drives and their associated computer storage media discussed aboveand illustrated in FIG. 8, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 810. In FIG. 8, for example, hard disk drive 841 is illustratedas storing operating system 844, application programs 845, other programmodules 846, and program data 847. Note that these components can eitherbe the same as or different from operating system 834, applicationprograms 835, other program modules 836, and program data 837. Operatingsystem 844, application programs 845, other program modules 846, andprogram data 847 are given different numbers here to illustrate that, ata minimum, they are different copies. A user may enter commands andinformation into the computer 810 through input devices such as akeyboard 862 and pointing device 861, commonly referred to as a mouse,trackball or touch pad. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite dish, scanner, or the like.These and other input devices are often connected to the processing unit820 through a user input interface 860 that is coupled to the systembus, but may be connected by other interface and bus structures, such asa parallel port, game port or a universal serial bus (USB). A monitor891 or other type of display device is also connected to the system bus821 via an interface, such as a video interface 890. In addition to themonitor, computers may also include other peripheral output devices suchas speakers 897 and printer 896, which may be connected through anoutput peripheral interface 895.

The computer 810 may operate in a networked environment using logicalconnections to one or more remote computers, such as a remote computer880. The remote computer 880 may be a personal computer, a server, arouter, a network PC, a peer device or other common network node, andtypically includes many or all of the elements described above relativeto the computer 810, although only a memory storage device 881 has beenillustrated in FIG. 8. The logical connections depicted in FIG. 8include a local area network (LAN) 871 and a wide area network (WAN)873, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

When used in a LAN networking environment, the computer 810 is connectedto the LAN 871 through a network interface or adapter 870. When used ina WAN networking environment, the computer 810 typically includes amodem 872 or other means for establishing communications over the WAN873, such as the Internet. The modem 872, which may be internal orexternal, may be connected to the system bus 821 via the user inputinterface 860, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 810, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 8 illustrates remoteapplication programs 885 as residing on memory device 881. It will beappreciated that the network connections shown are exemplary and othermeans of establishing a communications link between the computers may beused.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated that various alterations,modifications, and improvements will readily occur to those skilled inthe art.

Such alterations, modifications, and improvements are intended to bepart of this disclosure, and are intended to be within the spirit andscope of the invention. Further, though advantages of the presentinvention are indicated, it should be appreciated that not everyembodiment of the technology described herein will include everydescribed advantage. Some embodiments may not implement any featuresdescribed as advantageous herein and in some instances one or more ofthe described features may be implemented to achieve furtherembodiments. Accordingly, the foregoing description and drawings are byway of example only.

The above-described embodiments of the technology described herein canbe implemented in any of numerous ways. For example, the embodiments maybe implemented using hardware, software or a combination thereof. Whenimplemented in software, the software code can be executed on anysuitable processor or collection of processors, whether provided in asingle computer or distributed among multiple computers. Such processorsmay be implemented as integrated circuits, with one or more processorsin an integrated circuit component, including commercially availableintegrated circuit components known in the art by names such as CPUchips, GPU chips, microprocessor, microcontroller, or co-processor.Alternatively, a processor may be implemented in custom circuitry, suchas an ASIC, or semicustom circuitry resulting from configuring aprogrammable logic device. As yet a further alternative, a processor maybe a portion of a larger circuit or semiconductor device, whethercommercially available, semi-custom or custom. As a specific example,some commercially available microprocessors have multiple cores suchthat one or a subset of those cores may constitute a processor. However,a processor may be implemented using circuitry in any suitable format.

Further, it should be appreciated that a computer may be embodied in anyof a number of forms, such as a rack-mounted computer, a desktopcomputer, a laptop computer, or a tablet computer. Additionally, acomputer may be embedded in a device not generally regarded as acomputer but with suitable processing capabilities, including a PersonalDigital Assistant (PDA), a smart phone or any other suitable portable orfixed electronic device.

Also, a computer may have one or more input and output devices. Thesedevices can be used, among other things, to present a user interface.Examples of output devices that can be used to provide a user interfaceinclude printers or display screens for visual presentation of outputand speakers or other sound generating devices for audible presentationof output. Examples of input devices that can be used for a userinterface include keyboards, and pointing devices, such as mice, touchpads, and digitizing tablets. As another example, a computer may receiveinput information through speech recognition or in other audible format.

Such computers may be interconnected by one or more networks in anysuitable form, including as a local area network or a wide area network,such as an enterprise network or the Internet. Such networks may bebased on any suitable technology and may operate according to anysuitable protocol and may include wireless networks, wired networks orfiber optic networks.

Also, the various methods or processes outlined herein may be coded assoftware that is executable on one or more processors that employ anyone of a variety of operating systems or platforms. Additionally, suchsoftware may be written using any of a number of suitable programminglanguages and/or programming or scripting tools, and also may becompiled as executable machine language code or intermediate code thatis executed on a framework or virtual machine.

In this respect, the invention may be embodied as a computer readablestorage medium (or multiple computer readable media) (e.g., a computermemory, one or more floppy discs, compact discs (CD), optical discs,digital video disks (DVD), magnetic tapes, flash memories, circuitconfigurations in Field Programmable Gate Arrays or other semiconductordevices, or other tangible computer storage medium) encoded with one ormore programs that, when executed on one or more computers or otherprocessors, perform methods that implement the various embodiments ofthe invention discussed above. As is apparent from the foregoingexamples, a computer readable storage medium may retain information fora sufficient time to provide computer-executable instructions in anon-transitory form. Such a computer readable storage medium or mediacan be transportable, such that the program or programs stored thereoncan be loaded onto one or more different computers or other processorsto implement various aspects of the present invention as discussedabove. As used herein, the term “computer-readable storage medium”encompasses only a non-transitory computer-readable medium that can beconsidered to be a manufacture (i.e., article of manufacture) or amachine. Alternatively or additionally, the invention may be embodied asa computer readable medium other than a computer-readable storagemedium, such as a propagating signal.

The terms “program” or “software,” when used herein, are used in ageneric sense to refer to any type of computer code or set ofcomputer-executable instructions that can be employed to program acomputer or other processor to implement various aspects of the presentinvention as discussed above. Additionally, it should be appreciatedthat according to one aspect of this embodiment, one or more computerprograms that when executed perform methods of the present inventionneed not reside on a single computer or processor, but may bedistributed in a modular fashion amongst a number of different computersor processors to implement various aspects of the present invention.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, data structures may be stored in computer-readable media in anysuitable form. For simplicity of illustration, data structures may beshown to have fields that are related through location in the datastructure. Such relationships may likewise be achieved by assigningstorage for the fields with locations in a computer-readable medium thatconveys relationship between the fields. However, any suitable mechanismmay be used to establish a relationship between information in fields ofa data structure, including through the use of pointers, tags or othermechanisms that establish relationship between data elements.

Various aspects of the present invention may be used alone, incombination, or in a variety of arrangements not specifically discussedin the embodiments described in the foregoing and is therefore notlimited in its application to the details and arrangement of componentsset forth in the foregoing description or illustrated in the drawings.For example, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments.

Also, the invention may be embodied as a method, of which an example hasbeen provided. The acts performed as part of the method may be orderedin any suitable way. Accordingly, embodiments may be constructed inwhich acts are performed in an order different than illustrated, whichmay include performing some acts simultaneously, even though shown assequential acts in illustrative embodiments.

Further, some actions are described as taken by a “user.” It should beappreciated that a “user” need not be a single individual, and that insome embodiments, actions attributable to a “user” may be performed by ateam of individuals and/or an individual in combination withcomputer-assisted tools or other mechanisms.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

Also, the phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting. The use of“including,” “comprising,” or “having,” “containing,” “involving,” andvariations thereof herein, is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

What is claimed is:
 1. An additive fabrication device configured toproduce three-dimensional objects by sintering a source material, thedevice comprising: a material deposition mechanism; a fabrication bedconfigured to receive source material from the material depositionmechanism; a heater configured to move over the fabrication bed and todirect heat onto the source material deposited by the materialdeposition mechanism; and an energy source configured to be directedonto the deposited source material heated by the heater to causesintering of the heated deposited source material.
 2. The additivefabrication device of claim 1, wherein the material deposition mechanismis configured to move over the fabrication bed at the same time as theheater moves over the fabrication bed.
 3. The additive fabricationdevice of claim 2, wherein the material deposition mechanism and theheater are mechanically coupled to an assembly, at least part of whichis configured to move over the fabrication bed, and wherein the materialdeposition mechanism and the heater are configured to move over thefabrication bed via their coupling to the assembly.
 4. The additivefabrication device of claim 3, wherein the assembly is configured tomove over the fabrication bed such that the heater trails the materialdeposition mechanism during deposition of the source material.
 5. Theadditive fabrication device of claim 3, wherein the heater is coupled tothe assembly in proximity to the material deposition mechanism.
 6. Theadditive fabrication device of claim 1, further comprising a temperaturesensor arranged to sense a temperature of the source material depositedby the material deposition mechanism.
 7. The additive fabrication deviceof claim 6, wherein the temperature sensor is coupled to the assembly.8. The additive fabrication device of claim 6, wherein the heater isconfigured to operate at a temperature based at least in part on thetemperature of the source material sensed by the temperature sensor. 9.The additive fabrication device of claim 3, wherein the energy source iscoupled to the assembly.
 10. The additive fabrication device of claim 1,wherein the heater is a tube heater.
 11. The additive fabrication deviceof claim 3, wherein the assembly comprises a vertical axis and one ormore structures extending radially from the vertical axis that arepositioned over the fabrication bed, wherein the assembly is configuredto rotate about the axis causing the one or more structures to move overthe fabrication bed, and wherein the heater and material depositionmechanism are coupled to the one or more structures.
 12. The additivefabrication device of claim 11, wherein the energy source is coupled tothe one or more structures.
 13. The additive fabrication device of claim3, wherein the assembly is configured to rotate such that the one ormore structures move the coupled material deposition mechanism over thefabrication bed followed by the coupled heater over the fabrication bedfollowed by the coupled energy source over the fabrication bed.
 14. Theadditive fabrication device of claim 1, further comprising one or moreadditional heaters, material deposition mechanisms and/or energysources.
 15. The additive fabrication device of claim 1, wherein theenergy source comprises a laser.
 16. A method of fabricating an objectvia additive fabrication, said additive fabrication comprising sinteringa source material, the method comprising: moving a material depositionmechanism over a fabrication bed and operating the material depositionmechanism to deposit source material onto the fabrication bed; directingheat from the heater onto the source material deposited by the materialdeposition mechanism by moving a heater over the fabrication bed; andsintering the heated deposited source material by directing an energysource onto the deposited source material heated by the heater.
 17. Themethod of claim 16, wherein the material deposition mechanism moves overthe fabrication bed at the same time as the heater moves over thefabrication bed.
 18. The method of claim 17, wherein the materialdeposition mechanism and the heater are mechanically coupled to anassembly, at least part of which moves over the fabrication bed suchthat the material deposition mechanism and the heater move over thefabrication bed via their coupling to the assembly.
 19. The method ofclaim 18, wherein the assembly moves over the fabrication bed such thatthe heater trails the material deposition mechanism during deposition ofthe source material.
 20. The method of claim 16, wherein the heater isoperated at a temperature based at least in part on a temperature of thesource material sensed by a temperature sensor.
 21. The method of claim18, wherein the assembly rotates such that the one or more structuresmove the coupled material deposition mechanism over the fabrication bedfollowed by the coupled heater over the fabrication bed followed by thecoupled energy source over the fabrication bed.